GAZA/JERUSALEM — Israel resumed air strikes in the Gaza Strip on Tuesday, six hours after agreeing to an Egyptian-proposed truce that failed to halt Hamas rocket attacks.

"Hamas has fired 47 rockets since we suspended our strikes in Gaza (this morning). As a result, we have resumed our operation against Hamas," an Israeli military statement said.

Under a blueprint announced by Egypt — Gaza's neighbor and whose military-backed government has been at odds with Hamas Islamists — a mutual "de-escalation" of week-old fighting was to have begun at 9 a.m., with hostilities ceasing within 12 hours.

Hamas' armed wing, the Izz el-Deen al-Qassam Brigades, rejected the ceasefire, saying its battle with Israel would "increase in ferocity and intensity".

But Moussa Abu Marzouk, a top Hamas official who was in Cairo, had said the movement, which is seeking a deal that would ease border restrictions imposed by both Egypt and Israel, had made no final decision on the proposal.

Live television showed Israel's Iron Dome anti-missile system intercepting several rockets over the port city of Ashdod, where a factory was hit. Emergency services said no one was hurt.

Sirens also sounded in areas up to 130 kilometers (80 miles)north of the Gaza Strip. The Qassam Brigades claimed responsibility for some of the rocket launchings.

Speaking in Vienna, U.S. Secretary of State John Kerry supported Israel: "I cannot condemn strongly enough the actions of Hamas in so brazenly firing rockets, in multiple numbers, in the face of a goodwill effort (to secure) a ceasefire."

Gaza health officials said at least 184 Palestinians, most of them civilians, have been killed in eight days of fighting, the worst Israel-Palestinian flare-up in two years.

Prime Minister Benjamin Netanyahu, whose security cabinet voted 6-2 earlier on Tuesday to accept the truce, had cautioned that Israel would respond strongly if rockets continued to fly.

An Israeli official, speaking as the Israeli strikes resumed, said: "The prime minister and the defense minister have ordered the Israeli armed forces to take powerful action against terrorist targets in Gaza."

Earlier, Sami Abu Zuhri, a Hamas spokesman in Gaza, said that demands the movement has made must be met before it lays down its weapons.

Other Palestinian militant groups - Islamic Jihad, the Popular Front for the Liberation of Palestine and the Democratic Front for the Liberation of Palestine - also said they had not yet agreed to the Egyptian offer.

Palestinian President Mahmoud Abbas, who reached an agreement with Hamas in April that led to the formation of a unity government last month, urged acceptance of the proposal, the official Palestinian news agency WAFA said.

Amos Gilad, a senior Israeli defense official and envoy to Cairo, told Israel's Army Radio that Hamas had been weakened by the air and sea bombardment of Gaza, having tried "every possible means of striking at Israel."

Hundreds of rockets fired at Israel have caused no fatalities, largely due to Iron Dome. But the strikes are a threat that send people rushing into shelters.

Israel had mobilized tens of thousands of troops for a threatened Gaza invasion if the rocket salvoes persisted.

"We still have the possibility of going in, under cabinet authority, and putting an end to (the rockets)," Gilad said.

In overnight attacks before the brief ceasefire, Israel said it had bombed 25 sites in Gaza. Palestinian medical officials said a 63-year-old man and a 52-year-old woman were killed

Under the ceasefire proposal announced by Egypt's Foreign Ministry, high-level delegations from Israel and the Palestinian factions would hold separate talks in Cairo within 48 hours to consolidate the ceasefire with "confidence-building measures".

The surge in hostilities over the past week was prompted by the murder last month of three Jewish seminary students in the occupied West Bank and the revenge killing on July 2 of a Palestinian youth in Jerusalem.

Israel said on Monday three Jews in police custody had confessed to killing the Palestinian.

Hamas leaders have said a ceasefire must include an end to Israel's blockade of Gaza and a re-commitment to a truce reached in an eight-day war there in 2012. Hamas also wants Egypt to ease restrictions at its Rafah crossing with Gaza imposed after the military toppled Islamist president Mohammed Morsi last July.

The Egyptian proposal made no mention of Rafah or when restrictions might be eased.

Hamas has faced a cash crisis and Gaza's economic hardship has deepened as a result of Egypt's destruction of cross-border smuggling tunnels. Cairo accuses Hamas of aiding anti-government Islamist militants in Egypt's Sinai peninsula, an allegation the Palestinian group denies.

Hamas has said it also wants the release of hundreds of its activists arrested in the West Bank while Israel searched for the three missing teens.

Israel resumed air strikes in the Gaza Strip on Tuesday, six hours after agreeing to an Egyptian-proposed truce that failed to halt Hamas rocket attacks. "Hamas has fired 47 rockets since we suspended our strikes in Gaza (this morning)," an Israeli military statement said.